File:Priestley.jpg|thumb|250px|Priestley by Ellen Sharples (1794)
[McLachlan (1983), 28–30.]|alt=Quarter-length portrait of a man in a black coat against a purple and blue curtain backdrop.
'''Joseph Priestley''' (;
[[http://www.collinsdictionary.com/dictionary/american/priestley "Priestley"]: ''Collins English Dictionary'' – Complete & Unabridged 2012 Digital Edition.]
– 6 February 1804) was an 18th-century English theologian, English Dissenters|dissenting
clergyman, Natural philosophy|natural philosopher
, educator, and Liberalism|Liberal Political philosophy|political theorist
who published over 150 works. He is usually credited with the discovery of oxygen
having isolated it in its gaseous state, although...